The seal of the bearing can be divided into two types: self-sealing and external seal. The so-called bearing self-sealing is to make the bearing itself with sealing performance device. such as bearing with dust cover, sealing ring, etc. This seal occupies a small space, easy installation and disassembly, the cost is relatively low. The so-called bearing plus sealing performance device, is in the installation of the end of the internal system to create a variety of properties of the sealing device. The bearing plus seal is divided into non-contact seal and contact type seal. The Non-contact seal is suitable for high speed and high temperature occasions, with different structure forms, such as Gap type, labyrinth type and washer type. Contact seal is suitable for medium and low speed working conditions, commonly used in the form of felt seal and bowl seal.

According to the working condition of the bearing and the requirement of the working environment to the sealing degree, it is often used in the engineering design to synthesize various sealing forms to achieve better sealing effect. The following major factors should be considered in the selection of the bearing plus seals:

Bearing lubricants and types (grease and lubricants);

The working environment of the bearing and the size of the space occupied;

The bearing structure of the shaft has the advantages of allowing angular deviation;